1G MPI relay intermittent failing?

[KFred 513]

Ill try to keep this short. The other day my car started to hit a wall at 3500 rpm. It felt like timing was being pulled. Then after work the car ran fine. The next morning the same thing happened and the car actually stalled and wouldn't start. I left it overnight, and it started again, still had the hesitation in the mid 3k rpm range, then stalled just before I made it home. After cooling for two hours the car started and i drove it into the garage. The car idled fine, with no misfires. I took a log and everything was normal.

I have an intermittent problem here that seems to be heat triggered. I'm leaning towards my fuel pump relay even though nobody has seemed to have trouble with one ever .

I know than i won't get a simple reply that will get me running, but im looking to see if anyone has ideas for what it could be.

I pulled the fuel pump and the tank is clean.
Gas at the rail is also clean.
I replaced the PTU but that didn't help.
My temp sensor was working throughout the trouble.
Ecu has no leaking caps and my CEL cycles as it should with key

Weird symptoms i can't explain:

For months, under hard acceleration in 1st and 2nd my tach would rise to about 4-5k then swing down to 1k then back up to 7-8k, but I could never hit a first gear shift bc of it

When my car isn't running, sometimes my rpm will show 200-700 on a datalog with link. Is this a sign of something to be concerned with? My tach doesn't show rpm, but the ecu must be.

 

[KFred 513]

So a short update:

I swapped in a working walbro 255 but it did not help me.
I also got my alternator tested but that didnt help either.

I'm now thinking it is either the CAS. I need to find one to swap in.

Any ideas about what could be causing this?

 

[wrencher]

How bout when the no start is current, test for spark, fuel pressure & injector pulse?
See what it is loosing to at least narrow down the list of suspects.